Yea some quantum or string theory bit would need to be involved. If u had something 180k+ gs any where near earth it would rip the planet apart due to gravimetric distortion and relative densities. (Like as close as the traveler is) that or you would need an anti gravity field (which isnt impossible, we jus got absolutely no idea how the physics let alone mechanics of one actually works so far) Neutronium (the depleted core of neutron stars) is basically a diamond but instead of carbon being its main elemental build, its the heavier elements such as iron and cobalt.